This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Study to Evaluate Safety and Immunogenicity of Trivalent Influenza Vaccine, Formulation 2015 Southern Hemisphere, When Administered to Healthy Adult Subjects. (NCT02427750), a na phase 2 study. The primary outcome is Percentages of Subjects With Single Radial Hemolysis (SRH) Areas ≥25mm^2, Against Each of Three Vaccine Strains After Receiving One Dose of TIV..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02427750 |
| Phase | Phase 2 |
| Condition | Human Influenza |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 126 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Novartis |
| Results posted | Yes |
2. Clinical Question
Population
Healthy adults in two age cohorts: 18 to ≤60 years and ≥61 years. The registry record lists 126 participants enrolled, with 63 participants in each age-cohort safety group.
Intervention
One injection of Agrippal®, a surface-antigen, inactivated, egg-derived trivalent influenza vaccine using the 2015 Southern Hemisphere formulation.
Comparator
There was no separate control group. This was a single-arm study, and the allocation field is recorded as not applicable.
Primary question
What proportion of participants in each age cohort had SRH areas ≥25mm^2 against each of the three vaccine strains after one dose? The endpoint description specifies assessment three weeks after vaccination; numerical results are not reported in the registry record.
The study was designed to assess safety and immunogenicity, rather than to compare the vaccine with another vaccine or with no vaccination. Immunogenicity refers to the immune response measured by the study’s laboratory assay. The registry describes SRH or HI testing at approximately 21 days post vaccination, while the primary endpoint is stated in terms of SRH areas at Day 1 and Day 22 post vaccination.
The registry also gives age-specific CHMP criteria for the proportion achieving the stated SRH threshold: >70% for adults aged 18 to ≤60 years and >60% for subjects aged ≥61 years. These are criteria described in the record, not reported study findings. Because the endpoint estimates for the age groups and vaccine strains are not reported, the record does not establish whether either criterion was met.
3. Trial Design
This was a Phase II, open-label, single-arm, multicenter study of trivalent influenza vaccine in healthy adults. It is recorded as completed. Enrollment was 126. The study description identifies two age cohorts: 18 to ≤60 years and ≥61 years. The safety groups list 63 participants in each cohort.
Participants received one injection of Agrippal®, described as a surface-antigen, inactivated, egg-derived trivalent influenza vaccine. Its formulation was based on the WHO-recommended influenza strains for the 2015 Southern Hemisphere vaccine. The registry says the study was intended to evaluate safety and immunogenicity and that its data were intended to support use of the vaccine in future influenza seasons if the recommended composition remained the same.
Open-label means that masking was not used, consistent with the registry’s masking entry of none. The study had a single group rather than randomized treatment arms. Therefore, the design can describe outcomes among participants who received the vaccine, but it does not provide a concurrent control group for estimating a difference between treatments. The allocation field is recorded as not applicable, and the registry notes that this is not a randomized comparison.
The record lists a start of 2015-04 and primary completion of 2015-05. The immunogenicity description refers to post-vaccination assessment at approximately 21 days; the primary endpoint timeframe is specified as Day 1 and Day 22 post vaccination. The primary endpoint analysis population is described as the per-protocol population. The registry record does not report the detailed criteria for inclusion in that population or the numbers included in its endpoint analyses.
The record does not report a statistical analysis plan, a sample-size justification for the trial, or interim analyses. The completed status and enrollment count describe the study record, but they do not supply the missing endpoint estimates.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: All enrolled subjects were included in the trial.
Overall Study
| Stage | TIV (18 to ≤ 60 Years) | TIV (≥ 61 Years) |
|---|---|---|
| STARTED | 63 | 63 |
| COMPLETED | 63 | 63 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: The analysis was performed on the per-protocol population (PP).
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | TIV (18 to ≤ 60 Years) | TIV (≥ 61 Years) | Total |
|---|---|---|---|---|
| Participants analysed | 63 | 63 | 126 | |
| Age, Continuous | years | 32.1 (SD 11.0) | 69.3 (SD 6.9) | 50.7 (SD 20.8) |
| Sex: Female, Male: Female | Participants | 55 | 52 | 107 |
| Sex: Female, Male: Male | Participants | 8 | 11 | 19 |
6. Primary Endpoint
The registry lists the primary outcome as Percentages of Subjects With Single Radial Hemolysis (SRH) Areas ≥25mm^2, Against Each of Three Vaccine Strains After Receiving One Dose of TIV., measured over Day 1 and Day 22 post vaccination.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | Percentages of subjects |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the percentage of subjects in each age group with SRH areas ≥25mm^2 against each of the three vaccine strains after one dose of trivalent influenza vaccine. SRH, or Single Radial Hemolysis, is one of the antibody-response methods named in the record; HI, or Hemagglutination Inhibition, is also identified as an immunogenicity assay. The endpoint description focuses specifically on the SRH threshold.
In general, a proportion above a prespecified assay threshold provides a way to describe how many participants reached a defined level of measured antibody response. Reporting the percentage separately by age cohort and strain allows the response pattern to be considered across the study’s age groups and the three vaccine components. This is a descriptive immunogenicity measure; it is not itself a direct measure of clinical protection.
The registry states that the response was assessed three weeks after vaccination and gives Day 1 and Day 22 post vaccination as the primary endpoint timeframe. It also describes CHMP criteria of >70% for adults aged 18 to ≤60 years and >60% for subjects aged ≥61 years. Those thresholds are benchmarks named in the record, not observed percentages.
The registry record does not report the percentages, confidence limits, or strain-specific estimates for this endpoint. Consequently, the extent and precision of the measured responses, and whether the stated criteria were met, are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The study’s stated primary outcome is an age-specific percentage meeting an SRH threshold for each vaccine strain. The record explains what was to be measured and identifies the relevant post-vaccination timepoint, but it does not report the resulting percentages or confidence intervals. It is therefore not possible to describe the magnitude or precision of the primary immunogenicity findings from the registry record.
The registry lists the per-protocol population as the population used for the primary analysis. Per-protocol analyses generally focus on participants who meet specified study requirements, but the detailed requirements and analysis counts are not reported in the registry record. Without those counts, it is not possible to determine how the analyzed population relates to the enrolled groups or whether exclusions affected the estimates.
The record gives age-specific CHMP criteria: >70% for adults aged 18 to ≤60 years and >60% for subjects aged ≥61 years. These criteria give context for interpreting a reported percentage, but the record does not include the percentage estimates needed to make that comparison. A benchmark alone is not evidence that a result reached it.
The single-arm, open-label design is important when interpreting any reported outcomes. It can describe immunogenicity and safety observations among participants receiving the vaccine, but the absence of a concurrent comparator means it cannot estimate a relative effect against another vaccine or an untreated group. The study was not a randomized comparison; no causal contrast between treatment groups is reported.
The safety information lists zero participants affected by serious adverse events in each age-cohort group. This is a count in the registry record, not a comparison with another group and not proof that serious events cannot occur. The record separately lists other adverse events, but the serious-event count should not be conflated with those broader events. Death counts are not reported in the registry record.
Overall, the posted record supports a description of the study design, target population, endpoint definition, and recorded safety counts. It does not support conclusions about the observed immunogenicity percentages, their uncertainty, or whether the age-specific criteria were satisfied. No efficacy endpoint is reported in the registry record for this analysis, and the immunogenicity endpoint should not be recast as a clinical outcome.
9. Statistical Methods Explained
The registry describes a percentage endpoint, a per-protocol analysis population, and a 95% confidence interval as the stated dispersion measure. It does not report the numerical endpoint estimates or the statistical procedures used to calculate them. The explanations below distinguish the general meaning of these methods from what can be established about this particular study.
What does a percentage endpoint represent?
In general, a percentage expresses the share of an analyzed group that meets a defined outcome. Here the outcome is having an SRH area ≥25mm^2 against a vaccine strain. The percentage is intended to be assessed separately for the age cohorts and strains. Its interpretation depends on the people included in the analysis and on consistent application of the assay threshold. The registry identifies the per-protocol population but does not report the analysis denominator for each estimate, so the numerical percentage calculations cannot be reconstructed from the record.
The endpoint uses a threshold rather than describing the full distribution of assay measurements. In general, thresholding can make a result easier to compare with a stated benchmark, but it does not show how far individual measurements lie above or below the threshold. It also does not replace the need to report the estimate and its uncertainty. Neither the strain-specific percentages nor the underlying assay distributions are reported in the registry record.
How should a confidence interval be understood?
In general, a confidence interval gives a range of values compatible with an estimate under the statistical method used. It communicates precision: a narrower interval indicates less sampling uncertainty under that method, while a wider interval indicates more. It does not resolve systematic limitations such as selection, measurement, or the absence of a control group. The primary outcome lists a 95% confidence interval as its dispersion measure, but the numerical intervals and the method used to construct them are not reported in the registry record.
When a percentage is compared with a benchmark, the point estimate and its uncertainty provide different information. A point estimate describes the observed proportion; an interval indicates the precision around that estimate. The registry names the CHMP thresholds but provides neither the observed estimates nor their intervals. It is therefore not possible to determine how close an estimate might have been to a threshold or how precise it was.
What does the design allow?
In general, a single-arm study can estimate outcomes among the participants receiving the intervention. Without a concurrent comparison group, it cannot estimate the contrast between that intervention and another treatment under the same study conditions. Open-label status means masking was not used, as stated in the registry. These design features do not invalidate descriptive observations, but they limit what can be inferred from comparisons with external expectations or other studies.
Because the allocation is recorded as not applicable and the model is single group, the two age cohorts are not randomized treatment arms. They are age-defined groups within the study. Differences between their outcomes, if reported, would not by themselves establish that age caused a difference; other group characteristics and uncertainty would also matter. The registry does not report an adjusted analysis or a formal comparison between the cohorts.
What is known about planning calculations?
The record describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect, and that non-time-to-event illustrations are expressed as participants per arm for 80% power or other stated power targets. These are planning illustrations, not observed power, and they do not describe the enrollment design of this single-arm trial. Numerical planning results are not reported in the registry record. The record also does not report the trial’s own sample-size justification or show that these illustrations were used to plan the study.
More generally, power calculations concern the probability of detecting a specified effect under assumed conditions. They are sensitive to the assumed effect, variability, significance level, allocation, and analysis method. A planning calculation cannot substitute for an observed treatment comparison, particularly when a study has no control arm. Since the underlying observed endpoint estimates are not reported, the planning illustrations cannot be independently interpreted from the registry record.
The record lists no registry analyses. It does not state whether any formal hypothesis tests were performed, how missing assay measurements were handled, or whether confidence intervals were adjusted for multiple strain and age-cohort evaluations. Those methods should not be inferred from the endpoint description alone.
10. Multiplicity, Missing Data and Analysis Populations
The primary endpoint involves three vaccine strains and two age cohorts. Considering several strain-by-cohort results raises a general multiplicity question: when many estimates or tests are examined, the chance of at least one apparently notable result can increase if each is assessed independently. The registry record does not report a multiplicity adjustment, a testing hierarchy, or a plan identifying one strain or cohort as more important than the others. It also does not report formal hypothesis tests for the primary endpoint.
The registry names age-specific CHMP criteria, but does not explain whether those criteria were intended as separate assessments or how uncertainty across strains and cohorts was to be handled. The criteria alone do not establish a statistical testing procedure. Numerical endpoint estimates and confidence intervals are not reported, so no assessment of these criteria or of the joint evidence across outcomes is possible from the record.
The endpoint population is described as per-protocol. The record does not report how many participants contributed to each immunogenicity estimate, the criteria for per-protocol inclusion, or whether all enrolled participants had usable assay measurements. Missing-data handling, including any imputation or sensitivity analysis, is not reported in the registry record.
Those omissions matter because the analysis population and missing measurements can affect the interpretation of a percentage. In general, excluding participants with unavailable measurements may lead to a different estimate than analyzing all enrolled participants, depending on why data are missing. That possibility cannot be quantified for this study because the relevant counts and reasons are not reported. The registry also does not describe a separate intention-to-treat analysis or other analysis populations.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| TIV (18 to ≤ 60 Years) | 0 | 63 | 0.0% |
| TIV (≥ 61 Years) | 0 | 63 | 0.0% |
| Total | 0 | 126 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| TIV (18 to ≤ 60 Years) | 27 of 63 |
| TIV (≥ 61 Years) | 33 of 63 |
| Total | 60 of 126 |
Most frequent non-serious adverse event terms
| Event term | Organ system | TIV (18 to ≤ 60 Years) | TIV (≥ 61 Years) | Total |
|---|---|---|---|---|
| HEADACHE | Nervous system disorders | 14 of 63 | 12 of 63 | 26 of 126 |
| INJECTION SITE PAIN | General disorders | 14 of 63 | 9 of 63 | 23 of 126 |
| MYALGIA | Musculoskeletal and connective tissue disorders | 7 of 63 | 6 of 63 | 13 of 126 |
| INJECTION SITE INDURATION | General disorders | 4 of 63 | 8 of 63 | 12 of 126 |
| INJECTION SITE ERYTHEMA | General disorders | 4 of 63 | 7 of 63 | 11 of 126 |
| FATIGUE | General disorders | 6 of 63 | 4 of 63 | 10 of 126 |
| ARTHRALGIA | Musculoskeletal and connective tissue disorders | 3 of 63 | 5 of 63 | 8 of 126 |
| CHILLS | General disorders | 2 of 63 | 4 of 63 | 6 of 126 |
The registry lists 63 participants at risk for serious adverse events in each age-cohort group and records zero affected in each. The total row records 126 at risk and zero affected. These are registry counts; they are not estimates of comparative risk because the study has no separate control group.
The record lists 27 participants affected by other adverse events in the 18 to ≤60 years group and 33 in the ≥61 years group. These broader counts are distinct from the serious adverse event counts. The registry does not provide serious adverse event terms, and the deaths field is not reported in the registry record.
A zero recorded count means no affected participants were listed for that category in the registry results; it should not be interpreted as proof that the event is impossible or that risk is absent. The record does not provide further details about event definitions, duration of safety follow-up, severity grading, or the relationship of individual events to vaccination. Those details are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The study addresses whether an antibody response meeting a specified SRH threshold was measured after one dose of the 2015 Southern Hemisphere trivalent influenza vaccine in healthy adults, considered by age cohort and vaccine strain. It also records safety counts. This is a description of the study’s purpose and outcome framework, not a conclusion about the observed immunogenicity response.
The primary endpoint results are not reported in the registry record. As a result, the record does not show the proportions of participants meeting the threshold, the confidence intervals around those proportions, or whether the CHMP criteria were reached. The stated age-specific benchmarks cannot be treated as findings. No claim about the size or precision of the immune response can be made from the endpoint definition alone.
The single-arm design also defines what the findings could mean even if estimates were reported. Outcomes among vaccine recipients could be described, but without a concurrent control group the study cannot establish a comparative effect versus another vaccine or no vaccination. The age cohorts are not randomized comparison groups, so differences between them would require cautious interpretation.
The serious adverse event counts are recorded as zero affected in both age groups, while other adverse event counts are also listed. These observations describe the registry’s recorded safety data; they do not demonstrate absence of risk. The record does not provide event-level detail or report deaths.
The study’s stated intention was to evaluate safety and immunogenicity and to support future use if the recommended vaccine composition remained the same. That stated purpose does not itself establish that the results supported such use. The registry record does not report the primary numerical results needed to assess immunogenicity against the named criteria, nor does it report a controlled comparison or a clinical efficacy outcome. Any interpretation should remain within those limits.
13. Why This Trial Matters Statistically
Statistically, this study illustrates the difference between defining an endpoint and reporting its result. The registry specifies a threshold-based immunogenicity measure, its age cohorts, the vaccine strains, a post-vaccination assessment timeframe, and the intended per-protocol population. These details make the planned question understandable, but without the endpoint estimates and confidence intervals the strength and precision of the observed evidence cannot be assessed.
The age-specific criteria give the outcome a stated interpretive context. However, benchmarks and observed estimates are separate pieces of information. A threshold does not show whether participants reached it, and it does not reveal uncertainty around an estimate. The numerical immunogenicity findings are not reported in the registry record, so the comparison with those criteria remains unresolved.
The design also provides a useful statistical distinction. A single-arm study can describe measured responses and recorded adverse events among participants receiving an intervention. It does not have the structure required for a randomized between-treatment comparison. Age-group descriptions should likewise not be mistaken for randomized contrasts.
Finally, this record highlights the importance of analysis transparency. The per-protocol population is named, but its criteria and analysis counts are not reported. The record does not describe missing-data methods, multiplicity handling, or the statistical procedures used for confidence intervals. These omissions make it difficult to assess how the primary results would have been generated even if the estimates were present. Clear reporting of denominators, estimates, uncertainty, and analysis choices is essential for readers to evaluate immunogenicity evidence.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The principal limitation for interpreting this record is that the primary immunogenicity estimates are not reported. The endpoint definition, assay threshold, timepoint, and age-specific criteria are available, but no strain-specific percentages or confidence intervals are given. Thus, the key question the study was designed to address cannot be answered from the registry record.
The endpoint description mentions SRH or HI testing for immunogenicity, while the stated primary endpoint is based on SRH areas. The record does not clarify which assay contributed to each reported measure, and it does not include numerical assay outcomes. The stated timeframe includes Day 1 and Day 22 post vaccination, with the description also referring to assessment three weeks after vaccination.
The study was open-label and single-arm, with no randomized control group. Consequently, the design would not support a direct controlled comparison, and the age cohorts should not be treated as randomized arms. The registry does not report an adjusted analysis or a formal comparison between the age groups.
Although the per-protocol population is identified for the primary analysis, its membership criteria, group-specific denominators, and exclusions are not reported. Missing-data methods are also not described. The registry does not report whether multiplicity across strains and age cohorts was addressed, how confidence intervals were calculated, or whether hypothesis tests were conducted.
The safety record gives summary counts but no serious adverse event terms, event-level descriptions, or reported deaths. It does not describe follow-up duration for safety or provide detail that would allow assessment of individual events. The record’s completed status does not fill these reporting gaps, and no trial-specific sample-size justification or statistical analysis plan is reported in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Study to Evaluate Safety and Immunogenicity of Trivalent Influenza Vaccine, Formulation 2015 Southern Hemisphere, When Administered to Healthy Adult Subjects. — NCT02427750.
- Registry record last updated 2015-10-19; status last verified 2015-09.
- Results first posted 2015-10-19.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT02427750 is a completed Phase II, open-label, single-arm, multicenter study of one dose of Agrippal®, a trivalent influenza vaccine using the 2015 Southern Hemisphere formulation. It enrolled 126 healthy adults and described two age cohorts: 18 to ≤60 years and ≥61 years. The primary endpoint was the percentage with SRH areas ≥25mm^2 against each of three vaccine strains, assessed after vaccination; the primary analysis population was per-protocol.
The registry states age-specific CHMP criteria and lists safety counts, including zero participants affected by serious adverse events in each age-cohort group. However, the primary immunogenicity estimates and confidence intervals are not reported in the registry record. Detailed missing-data, multiplicity, and statistical analysis methods are also not reported.